Mass in the lung is very significant. CT scan
does not rule out cancer. You need a biopsy
You may have allergic component called eosinophilic pneumonia
which is benign condition. You need a biopsy either way through a bronchoscopy
( camera into the lung) or CT guided urgently. Are you a smoker, if yes and you are above the age of 35 you definitely need a biopsy. If you have PET scan access that will also help to decide what it could be. but the investigations which you have mentioned in your question definitely do not rule out serious conditions. Good luck.